Without an automated irrigation system, the height of plants two weeks after germination is normally distributed with a mean of 2.5 centimeters and a standard deviation of 0.5 centimeters.
a) What is the probability that a plant's height is greater than 2.25 centimeters?
b) What is the probability that a plant's height is between 2.0 and 3.0 centimeters?
c) What height is exceeded by 90% of the plants?